JP2660931B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and more particularly, to an image forming apparatus such as a toner image formed on an image carrier. The present invention relates to an image forming apparatus configured to transfer an image onto a transfer material held on a supporting member.

2. Description of the Related Art For example, in a color electrophotographic copying machine, an image is obtained by forming a toner image on an image carrier such as a photosensitive drum and transferring the toner image to a transfer material. Usually, the transfer material is carried and transported by a transfer drum configured by winding a transfer material carrying member, usually a transfer material carrying sheet such as a high-resistance film, around a drum-shaped frame. That is, the transfer material supplied to the transfer drum is mechanically fixed and held at the transfer material supply position by a gripper provided on a part of the peripheral surface of the transfer drum, or electrostatically attracted. It is wrapped around the transfer material carrying sheet depending on whether it is fixed and held by force.
-32079). Then, by rotating the transfer drum, the transfer material is transferred to the transfer position a plurality of times, and the toner images of a plurality of colors are transferred from the image carrier to the surface of the transfer material by the multiple transfer.

However, in the above-described conventional method, when the transfer material is held on the transfer material carrying sheet, a gap may be locally generated between the transfer material and the transfer material carrying sheet. The cause of such a gap is that the transfer material carrying sheet is, for example,
The transfer member is subjected to mechanical deformation by a cleaning member provided for cleaning and removing residual toner on the transfer material supporting sheet, or is affected by an electrostatic force caused by charging of the transfer material supporting sheet, or a transfer drum is provided. Is considered to be caused by deformation due to a thermal influence from a fixing device arranged in close proximity to the fixing device. In particular, when a corona charger is used as the transfer charger, a charge is applied to the transfer material and the transfer material carrying sheet in a relatively wide range, so that the deformation region of the transfer material carrying sheet is expanded.

In such a place where a gap is formed between the transfer material and the transfer material carrying sheet, the transfer efficiency is reduced, and the transfer is lost. If the transfer material holding surface of the transfer material holding sheet is deformed in a convex shape, so-called "jamming" is likely to occur. Conversely, if the transfer material holding surface is deformed in a concave shape, poor suction of the transfer material occurs. However, there arises a problem that a shift occurs at the time of transfer.

In particular, the above problem is remarkable when the transfer material is held on the transfer material carrying sheet by electrostatic attraction without using a gripper.

For this reason, conventionally, in an image forming apparatus that electrostatically transfers a toner image on an image carrier to a transfer material held on a transfer material carrier sheet to form an image on the transfer material, a transfer material carrier sheet is used. , The charge applying means contacting the transfer material carrying sheet and the attraction charging means contacting the transfer material on the holding surface of the transfer material carrying sheet are disposed facing each other. At least one of the pressure mechanisms is provided to forcibly remove a gap between the transfer material carrying sheet and the transfer material when the transfer material is attracted to the transfer material carrying sheet.

However, in the above-described conventional method, changes in temperature and humidity, changes in the thickness of the transfer material P, changes in the feed speed of the transfer material,
The transfer material is incompletely adsorbed to the transfer material supporting sheet between the transfer position and the position where the charge application device and the suction charging device are provided (that is, the transfer material supply position) due to the fluctuation of the charge of the charge applying device and the adsorption charging device. In many cases, the transfer material completely peels off from the transfer material carrying sheet to cause a jam. The incompletely adsorbed state means that a gap is locally formed between the transfer material and the transfer material carrying sheet. If the transfer material passes through the transfer position in this state, poor transfer or image misalignment occurs. Or, wrinkles or the like are generated on the transfer material. In particular, a transfer material having a curvature in a direction opposite to the curvature of the transfer material carrying sheet, that is, a so-called curled paper, has the above-described disadvantages.

Accordingly, an object of the present invention is to provide a transfer material carrying member such as a transfer material carrying sheet that carries and conveys a transfer material even if incomplete suction of the transfer material occurs between the suction position and the transfer position. It is an object of the present invention to provide an image forming apparatus capable of obtaining a high-quality image free from defects and further improving color reproducibility in color image formation.

Means for Solving the Problems The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides a transfer material carrying member for carrying a transfer material, a transfer means for transferring an image at a transfer position from an image carrier to a transfer material carried on the transfer material carrying member, and the transfer material carrying member An adsorbing and charging unit, which is provided so as to be capable of moving toward and away from the transfer member, and adsorbs and charges the transfer material supplied to the transfer material holding member at the transfer material supply position to the transfer material holding member. A guide member is provided downstream of the transfer material supply position and upstream of the transfer position in the moving direction of the support member, and guides the transfer material. An image forming apparatus, wherein the image forming apparatus is capable of moving toward and away from the transfer material supporting member independently of the moving toward and away from the supporting member.

Hereinafter, an image forming apparatus according to the present invention will be specifically described with reference to the drawings.

In FIG. 1, a photosensitive drum 1 as an image carrier is driven to rotate in the direction of an arrow. A primary charger 2, an optical system 3, a developing device 4, and a pre-transfer charger 5 are arranged in the rotation direction of the photosensitive drum 1 so as to face the outer peripheral surface of the photosensitive drum 1. The primary charger 2 applies a uniform charge amount to the photosensitive drum 1, and the optical system 3 applies a color-separated light image or a light beam L corresponding thereto to the surface of the photosensitive drum 1 at a predetermined timing, and Form an image.
For this optical system 3, a laser beam scanning device or the like is used. In this embodiment, the developing device 4 is a horizontally movable developing device that moves in a tangential direction opposite to the surface of the photosensitive drum 1, and includes a magenta developer, a cyan developer, a yellow developer, and a black developer. It is provided with four developing units 4M, 4C, 4Y and 4BK for storing the developer toners of the four colors, respectively. The developing device 4 causes the developing device selected in response to the light image of the selected color by the optical system 3 or the irradiation of the light beam L corresponding thereto to face the photosensitive drum 1, and a toner image is formed on the surface of the photosensitive drum 1. To form

Further, a transfer device 6 is provided to face the photosensitive drum 1. As schematically shown in FIG. 2, the transfer device 6 is a transfer drum in which a transfer material supporting member, that is, a transfer material supporting sheet 6a is cylindrically wound between cylindrical end frames 6b. or,
As shown in FIG. 1, at the transfer position facing the photosensitive drum 1, on the side opposite to the holding surface of the transfer material carrying sheet 6a,
That is, the transfer corona charger 7 is provided inside the transfer drum 6.

The transfer drum 6 is driven to rotate in the direction of the arrow, and on the upstream side of the transfer position where the corona charger 7 is disposed, on the opposite side of the transfer material holding surface of the transfer material supporting sheet 6a, that is, the transfer drum 6
Inside, a charging corona charger 19 is disposed, and a conductive roller 20 as a suction charging unit is disposed facing the transfer material holding surface.

Further, on the downstream side from the transfer position, corona dischargers 10 and 11 for removing static electricity are disposed with the transfer material supporting sheet 6a interposed therebetween, and the transfer material P held on the transfer material supporting sheet 6a is provided.
The pressing rollers 12, 13 for separating the transfer material from the transfer material supporting sheet 6a are disposed with the transfer material supporting sheet 6a interposed therebetween, and a separating blade 14 is disposed in the vicinity of the pressing rollers. Further downstream, a brush roller 15 for cleaning the holding surface of the transfer material carrying sheet 6a, and if necessary, a corona discharger or a brush type remover for removing adhesive force (residual Coulomb force and van der Waals force). An electric device 16 is provided.

Further, a fixing device 18 composed of a pair of fixing rollers is disposed adjacent to the transfer drum 6, and the toner image on the transfer material P separated from the transfer material carrying sheet 6 a by the separation blade 14 and conveyed by the conveyor 17. To establish.

Further, as shown in FIG. 1, around the photosensitive drum 1, there are provided a static eliminator 27 for removing electrostatic charges on the surface of the photosensitive drum 1, and a cleaning blade 28 for removing residual toner.
If necessary, a corona discharger 29 is provided near the separation blade 14 for the purpose of preventing image disturbance due to peeling discharge that occurs when the transfer material P is separated from the transfer material supporting sheet 6a. Then, it is preferable to perform AC corona discharge.

With such a configuration, the surface of the photosensitive drum 1 is
And then uniformly charged by the optical system 3
For example, when a color image passing through a green filter is irradiated, a latent image mainly composed of a magenta component is formed in the color image. The developing device 4 is synchronized with the feeding of the latent image.
Moves the developing device 4M containing the magenta developer in a tangential direction with respect to the photosensitive drum 1 so as to face the photosensitive drum 1 to form a magenta toner image on the photosensitive drum 1.

On the other hand, the transfer material P is introduced into the upper guide 22 and the lower guide 22 'by the movement of the registration rollers 21 and 21', and is guided by the upper and lower guides to form a conductive roller along the surface of the transfer material carrying sheet 6a. It is supplied to the transfer material supply position where 20 is located.

According to the present invention, the lower guide 22 'is supported swingably about the fulcrum A, and is normally urged clockwise by the coil spring 222 in FIG. The conductive roller 20 is rotatably attached to the tip of the vertical guide 22 '. Therefore, the conductive roller 20 is eccentrically driven to rotate in the direction of the arrow by a driving means (not shown). Cam221
When the lower guide 22 'swings around the fulcrum A, the lower guide 22' moves away from and to the transfer material carrying sheet 6a. Eccentric cam
221 is driven in synchronization with the supply timing of the transfer material P, and when the transfer material P is supplied to the supply position, the conductive roller 20 is moved to the transfer material carrying sheet 6a as shown in FIG. Positioned in contact.

In this embodiment, the transfer material P is transferred to the transfer material carrying sheet 6a.
In the position where the transfer material carrying sheet 6a is supplied, a distortion correcting means 23 composed of an elastic supporting member such as a 150 μm elastic sheet is provided on the surface opposite to the holding surface of the transfer material carrying sheet 6a so as to press and hold the transfer material carrying sheet 6a from the inside. This corrects or prevents mechanical deformation of the transfer material carrying sheet 6a by the brush roller 15 or deformation by the electrostatic force of the corona charger 19.

In this case, the elastic force of the straightening means 23 is
It is preferable to act in the direction in which the transfer material carrying sheet 6a is stretched, that is, in the direction opposite to the moving direction of the transfer material carrying sheet, thereby reducing distortion in the thrust direction (the axial direction of the transfer drum) of the transfer material carrying sheet 6a. be able to. In addition, corona charger 19
It is also possible to regulate the circumferential discharge distribution.

In the above configuration, after the transfer material P is supplied to the transfer material supply position where the conductive roller 20 is located, the transfer material P is electrostatically adsorbed and held on the transfer material supporting sheet 6a by the corona charger 19, and the photosensitive drum 1 Is transferred to the transfer position where the transfer charger 7 is located. Of course, the timing of the transfer of the transfer material by the registration rollers 21 and 21 'and the timing of the latent image formation by the optical system 3 are synchronized and coincide at the transfer position.

According to the present invention, a guide member for guiding a transfer material so as to be located between the transfer material supply position and the transfer position,
That is, a transfer material transport guide 223 is provided. In this embodiment, the transfer material transport guide 223 is formed integrally with the lower guide 22 '. Therefore, the transfer material P is now transferred to the transfer material carrying sheet 6a due to a change in the environment, a change in the thickness of the transfer material P or the like.
Even if a state in which the leading end of the transfer material P hangs down in the direction of gravity occurs without being held by suction, the transfer material P is guided by the transfer material transport guide 223 and is transferred to the transfer position without a jam state. You. The transfer material transport guide 223
Is rotated about the fulcrum A in the same manner as the lower guide, and when the conductive roller 20 is in contact with the surface of the transfer material carrying sheet 6a, it is slightly larger than the thickness of the transfer material P than the transfer material carrying sheet 6a. It is positioned and arranged so as to be separated by a large gap d.

At the transfer position, the corona charger 7 for transfer operates to generate a transfer electric field, and the toner image on the photosensitive drum 1 is transferred onto the transfer material P by the charge applied to the transfer material carrying sheet 6a.

According to the present embodiment, as shown in FIG.
When the rear end of the transfer material P passes through the conductive roller 20, the eccentric cam 221 is driven to rotate to the bottom dead center by the driving means. As a result, the lower guide 22 'is urged to rotate counterclockwise about the fulcrum A, and as a result, the conductive roller 20 and the transfer material transport guide 223 largely retreat from the transfer material carrying sheet 6a. As a result, dirt such as toner adhering to the transfer material carrying sheet is transferred to the conductive roller 20,
As a result, it is possible to prevent the transfer material P from being soiled.

The toner remaining on the photosensitive drum 1 after the transfer is removed by a charge eliminator.
After the charge is eliminated at 27, the charge is removed by the blade 28, and the surface of the photosensitive drum 1 is cleaned. On the other hand, the transfer material P adsorbed on the transfer material carrying sheet 6a moves with the rotation of the transfer drum 6 while carrying the toner image, and the corona discharge device
Pass between 10 and 11. At this time, the corona dischargers 10, 11
Is not energized. Further, the pressing rollers 12, 13 are also separated from the transfer material carrying sheet 6a, and the brush roller 15, the brush type static eliminator 16, and the conductive roller 20 are also provided on the transfer material carrying sheet 6a.
Away from 6a. Thus, the transfer material P transported without disturbing the toner image carried by the Coulomb force
Is further sent to the transfer position after passing between the corona charger 19 and the conductive roller 20.

The urging of the corona charger 19 and the contact of the conductive roller 20 with the transfer material carrying sheet 6a are completed before the leading end of the toner image of the transfer material P reaches the position of the corona charger 19 and the conductive roller 20. When passing through the gap, no charge for adsorption is applied to the transfer material P.

The above-described image forming and transferring operations are also performed for other cyan, yellow and black colors to form a full-color image on the transfer material P, and thereafter, the chargers 10, 11, 29 and separating means
By operating 12, 13, and 14, the transfer material P is separated from the transfer drum 6 and transported to the fixing device.

FIG. 4 shows another embodiment of the image forming apparatus according to the present invention.

The embodiment of FIG. 4 differs from the embodiment of FIG. 1 in the following points. In other words, in the present embodiment, the transfer material transport guide 223 formed integrally with the lower guide 22 ′, when the conductive roller 20 is in contact with the surface of the transfer material carrying
3a is configured to be in contact with the transfer material carrying sheet 6a.

Therefore, in this embodiment, since the substantially leading end 223a of the transfer material transport guide 223 and the transfer material carrying sheet 6a slide, the leading end 223a is desirably formed of, for example, an elastic sheet of 150 μm. .

As described above, according to the present embodiment, the transfer material carrying sheet 6a and the transfer material transport guide 223 are configured to be in contact with each other, so that an environmental change, a change in the state of the transfer material, and the like occur, and the transfer material P is Even if incomplete suction to the transfer material carrying sheet 6a occurs at the position 20, i.e., at the transfer material supply position, the transfer material P is reliably transferred to the transfer material carrying sheet 6a at the position of the substantially leading end 223a of the transfer material carrying guide 223. It can be adsorbed on the surface.

FIG. 5 shows still another embodiment. The embodiment shown in FIG. 5 is different from the embodiment shown in FIG.
It differs from 2 'in that it is provided independently.

In the embodiment of FIG. 5, the transfer material P is a conductive roller.
At the 20th position, the sheet is adsorbed on the transfer material carrying sheet 6a, and is then fed to the position of the transfer material transport guide 223. Transfer material transport guide 2
23 is fixed to an arm 25 pivotally supported on a frame 26 by a pin 26a. The arm 25 is normally held by a tension spring 30 so as to be separated from the transfer material carrying sheet 6a, and the transfer material transport guide 223 biases the electromagnetic solenoid 31 connected to the arm 25. By swinging the arm 25 against the elastic force of the extension spring 30, the arm 25 comes into contact with the transfer material carrying sheet 6a.

According to the present embodiment, when the transfer material P passes through the position of the transfer material transport guide 223, the transfer material transport guide 223 is brought into contact with the transfer material carrying sheet 6a, and otherwise, the transfer material P It is retracted to a position where it does not contact the sheet 6a.

Therefore, the transfer material P can be surely attracted to the transfer material carrying sheet 6a by the transfer material carrying guide 223 between the position of the conductive roller 20 and the transfer position, and the transfer material carrying sheet 223 uses toner of the transfer material carrying sheet. Dirt is transferred material transfer guide 22
Step 3 is performed, and as a result, the transfer material is prevented from being soiled.

Effect of the Invention As described above, the image forming apparatus according to the present invention has
Since the transfer material transport guide is provided between the transfer material supply position and the transfer position in the transfer material support member, even when incomplete suction of the transfer material to the transfer material support member occurs, the transfer material is transferred. The transfer material can be reliably transported to the transfer position by the transfer material transport guide even when it is likely to be completely separated from the material carrying member and a jam occurs, and high-quality images free of jams and transfer omissions can be obtained. In addition, in the case of forming a color image, there is an operational effect that color reproducibility can be improved. Further, according to the present invention, the transfer material transport guide for guiding the transfer material is configured to be capable of moving toward and away from the transfer material supporting member independently of the movement of the attraction / charging means toward and away from the transfer material supporting member. When the material passes through the transfer material transport guide position, the transfer material transport guide is brought into contact with the transfer material support member, and otherwise, the transfer material transport guide can be retracted to a position not in contact with the transfer material support member. The transfer guide can surely adsorb the transfer material to the transfer material carrying member, and also prevents the transfer material carrying member from being contaminated by toner or the like with the transfer material carrying guide, thereby preventing the transfer material from being soiled. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a perspective view of one embodiment of the transfer device. FIG. 3 is a schematic sectional view showing a mode in which the transfer material transport guide is separated from the transfer material carrying sheet in the image forming apparatus of FIG. 4 and 5 are schematic sectional views of another embodiment of the image forming apparatus according to the present invention. 1: Image carrier 6: Transfer device 7: Transfer charger 20: Charge injection means (conductor roller) 22, 22 ': Guide 221: Eccentric cam 223: Transfer material transport guide

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-120179 (JP, A) JP-A-59-24869 (JP, A) JP-A-60-14266 (JP, A) JP-A 57-120 99673 (JP, A)

Claims (1)

(57) [Claims] A transfer member configured to transfer an image at a transfer position from an image carrier to a transfer material supported by the transfer member; and a transfer member configured to contact the transfer member. An adsorbing and charging unit that is provided so as to be able to move away and that adsorbs and charges the transfer material supplied to the transfer material support member at the transfer material supply position to the transfer material support member. And a guide member provided downstream of the transfer material supply position and upstream of the transfer position in the moving direction of the transfer member, and configured to guide the transfer material. An image forming apparatus capable of moving toward and away from the transfer material supporting member independently of the movement toward and away from the transfer member.